Lighttpd is stated to outperform thttpd at between 2 and 5 times.
http://www.lighttpd.net/ - It has been used by TextDrive to handle a serious Slashdotting that killed their Apache server. Moving over to Lighttd allowed TextDrive to actually handle the hits coming from all those Slashdot.org eyeballs. Lighttpd is more likely to be used in full large scale FCGI load balanced production systems.